1. Field of the Invention
The present invention relates to a vortex flowmeter to be used in an internal combustion engine of a vehicle or the like to measure the quantity of a fluid, particularly with large turbulence.
2. Description of the Related Art
When a vortex flowmeter is used in an internal combustion engine of a vehicle or the like, it is always installed downstream of an air cleaner of the engine, as disclosed in the Japanese Patent Application Laid Open No. 58-21517 (1983) or the Japanese Patent Publication No. 62-26686 (1987), for example. In such structure, it is impossible to measure from low to high flow rate, with high precision, since the fluid flow is unstable. To solve this problem, it is proposed in the Japanese Patent Application Laid Open No. 61-134620 (1986), for example, to enhance the stability of vortex generation by arranging a turbulence generating element for generating turbulence in a part of the fluid upstream of the vortex generating column.
In such method, however, as described in the Japanese Patent Application Laid Open No. 57-67863 (1982), for example, the turbulence generating element possesses such a strong effect as to correct the vortex generating frequency, that is, the flow characteristics determined by the shape and width of the vortex generating column. Therefore, when vortexes generated by the turbulence generating element tend to be columnar and periodic, so-called Karman's vortex, the effect of the turbulence generating element on the flow characteristics is significant, and a precision is demanded strictly in the dimensions and arrangement of the turbulence generating element.